Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 180541

Area Forecast Discussion
National Weather Service Aberdeen SD
1241 AM CDT Fri Aug 18 2017

Issued at 846 PM CDT Thu Aug 17 2017

Disorganized convection continues its way east within the surface
trof across the bottom third of the CWA this evening. Within the
past couple of hours have begun to see a couple showers develop
north and east of Mobridge, likely forced by the northern extent
of this trof/boundary. Short range guidance continues to march
precipitation chances eastward across the cwa for several more
hours, so continuing with inherited pops adjusted slightly for
latest short range guidance trends. No plans to adjust overnight
low temperatures. Did also run the fog-tool and left in the mainly
"patchy fog" areal coverage it gave for the eastern half of the
cwa late tonight/early Friday morning out ahead of this surface

UPDATE Issued at 641 PM CDT Thu Aug 17 2017

See below for an aviation forecast discussion for the 00Z TAFs.


.SHORT TERM...(This Evening through Friday Afternoon)
Issued at 245 PM CDT Thu Aug 17 2017

Main forecast challenge in the near term is shower and thunderstorm
chances this evening. Weak upper level ridging currently over the
area will give way to a shortwave trough set to track through later
this evening and Friday. At the surface, a weak high pressure ridge
currently responsible for sunny skies will get pushed east by a low
pressure boundary approaching from the west. This low will become
the focus for shower and thunderstorm development beginning this
evening over parts of the western CWA, then dropping southeastward
through the overnight hours. There will be some shear to work with,
along with 7-8 C/km mid level lapse rates. Main hindering factor in
the potential for severe storms is the lack of instability, which
will be stronger south of the ABR CWA. Will however stick with
chance POPs across mainly the southwestern CWA this evening and into
the southeastern CWA later tonight. Looks to be a break in the
activity Friday morning, then daytime heating may allow for some
additional convective development across the far eastern CWA Friday

Low temperatures tonight will be mainly in the mid to upper 50s,
with highs on Friday ranging from the upper 70s east to the upper
80s southwest.

.LONG TERM...(Friday Evening through Thursday)
Issued at 245 PM CDT Thu Aug 17 2017

Much of the long term forecast is quiet, as an upper ridge moves
over the area to start the period, which keeps the upper jet
north of the area through the period. Could see a few lingering
showers Friday evening over western MN as the shortwave is
departs to the southeast, otherwise expect dry conditions. With
the upper ridge axis over the area on Saturday morning and
increasing southerly winds ahead of a cold front in the western
Dakotas, it looks like Saturday will be the warmest day of the
period. Deterministic and ensemble models consistent in highs
rising into the lower 90s over Central SD and into the 80s across
the rest of the CWA. The cold front looks to pass through the area
on Saturday night, but with limited upper level support/moisture,
expect a dry frontal passage. A weak high pressure ridge will
slide across the area behind the front (from a high centered in
ND), but with a weak shortwave and some 700-500mb
moisture/Q-Vector Convergence, would expect some 12-25kft clouds
to move east across at least the northern half of the CWA. With
the amount of forcing, wouldn`t be surprised to see some virga on
radar, but with dry air below 10kft, don`t expect any of it to
reach the ground.

The forecast becomes a little uncertain Sunday night into the
first part of next week. This is due to the varying ideas (both
timing/intensity) in the models on weak shortwaves moving through
the west-southwesterly flow over the region and when a weak
surface low develops in the Central Plains along the cold front
that pushed through the area Saturday night. Will likely be some
opportunities for clouds/rain during this period and will follow
a general blend of the models for now. The first day behind that
features (likely Tuesday) high pressure will move over the area
from Saskatchewan and should lead to a dry day. There will be
another opportunity for precip towards mid week as another cold
front drops southeast across the area in association with an
upper trough amplifying over the Great Lakes. As for temps next
week, expect them to be near or slightly below normal.


.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
Issued at 1226 AM CDT Fri Aug 18 2017

Isolated to scattered coverage of showers and thunderstorms is
evident on radar, and remains a possibility for the next few hours
at KABR and KATY, though limited coverage will preclude any
mention of thunder for those terminals. Generally expect VFR
conditions otherwise.




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